Propylene polymers for oriented films

ABSTRACT

This invention relates generally to crystalline polypropylene polymers and methods for their production. Specifically, this invention relates to crystalline polypropylene polymer compositions comprising both propylene homopolymers and propylene copolymers. The compositions are prepared using metallocene catalyst systems comprising at least two metallocenes in a polymerization process that involves the sequential or parallel polymerization of propylene homopolymers and copolymers using propylene with a small amount of comonomer, preferably ethylene. The resulting polymers are excellent for use in the production of biaxially oriented films. Films prepared with these propylene polymers have a significantly broader processability range and can be evenly stretched at lower temperature compared to films prepared from traditional polypropylene polymers.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. Ser. No. 08/916,699,filed Aug. 22, 1997, now abandoned, which claims priority to ProvisionalSerial No. 60/025,398, filed Sep. 4, 1996, the disclosures of which areincorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates generally to crystalline propylene polymercompositions, to methods for their production and to methods for theiruse in oriented film applications. Specifically, this invention relatesto crystalline propylene polymer compositions comprising both propylenehomopolymer and propylene copolymer components. Preferably the propylenepolymer composition is isotactic. The compositions are prepared usingmetallocene catalyst systems comprising at least two metallocenes in apolymerization process that involves the sequential or parallelpolymerization of propylene homopolymer and copolymer using propylenewith a small amount of comonomer, preferably ethylene. The resultingpolymer compositions are excellent for use in the production of orientedfilms. Films prepared with these propylene polymers have a significantlybroader processability range and can be evenly stretched at lowertemperature compared to films prepared from traditional propylene-basedpolymers.

BACKGROUND

[0003] Oriented polypropylene films are widely used in tape applicationsand in packaging applications such as food packaging. The optimizationof processing characteristics and film properties of propylene basedfilms has been the subject of intense effort. U.S. Pat. No. 5,118,566,for example, describes a biaxially oriented film made frompolypropylene, a natural or synthetic resin, and a nucleating agent. Theprocess for producing this film includes biaxially drawing the film attemperatures below the melting point of the polypropylene.

[0004] The present inventors have discovered crystalline propylenepolymer compositions made by polymerizing propylene in one stage andthen propylene and a minor amount of comonomer in a separate stage usinga metallocene catalyst system comprising at least two metallocenes ineach of the stages. The resulting polymers have surprisingly highmolecular weight and broad molecular weight distribution, and offerprocessability benefits in oriented film applications. Films made fromthese unique polymers have a significantly broader processability rangeand can be evenly stretched at lower temperatures compared to thepolypropylene films available today. The resulting films have afavorable balance of properties including high strength, good opticalproperties and good barrier properties.

[0005] Multiple stage polymerization processes are known in the art asis the use of multiple metallocenes, however, multiple stagepolymerization processes are usually used to prepare block copolymerswhich contain rubbery materials as opposed to the crystalline polymersof this invention. U.S. Pat. Nos. 5,280,074; 5,322,902, and 5,346,925,for example, describe two-stage processes for producing propylene blockcopolymers. The propylene/ethylene copolymer portion of thesecompositions is a non-crystalline, rubbery material suitable for moldingapplications rather than films. U.S. Pat. No. 5,350,817 and CanadianPatent Application No. 2,133,181 describe the use of two or moremetallocenes for the preparation of isotactic propylene polymers,however, neither reference describes a multiple stage process for theproduction of crystalline polymer compositions such as those describedherein.

SUMMARY

[0006] In one embodiment, the present invention provides for crystallinepropylene polymer composition comprising:

[0007] (a) from 10 to 90 weight percent of a crystalline propylenehomopolymer composition comprising a first propylene homopolymer and asecond propylene homopolymer; and

[0008] (b) from 90 to 10 weight percent of a crystalline propylenecopolymer composition comprising a first propylene copolymer and asecond propylene copolymer, the first propylene copolymer and secondpropylene copolymer comprising from 0.05 to 15 weight percent (based onthe total weight of the crystalline propylene polymer composition) of acomonomer;

[0009] wherein the crystalline propylene polymer composition has amolecular weight distribution (Mw/Mn) in the range of from 2.1 to 10;and

[0010] wherein the propylene homopolymer composition and the propylenecopolymer composition are obtained in separate stages using a singlemetallocene catalyst system comprising two different metallocenecatalyst components.

[0011] In another embodiment, the two different metallocenes catalystcomponents are represented by the formula:

[0012] wherein M is selected from the group consisting of titanium,zirconium, hafnium, vanadium niobium, tantalum, chromium, molybdenum andtungsten;

[0013] R¹ and R² are identical or different, are one of a hydrogen atom,a C₁-C₁₀ alkyl group, preferably a C₁-C₃ alkyl group, a C₁-C₁₀ alkoxygroup, a C₆-C₁₀ aryl group, a C₆-C₁₀ aryloxy group, a C₂-C₁₀ alkenylgroup, a C₂-C₄ alkenyl group, a C₇-C₄₀ arylalkyl group, a C₇-C₄₀alkylaryl group, a C₈-C₄₀ arylalkenyl group, or a halogen atom;

[0014] R³ and R⁴ are hydrogen atoms;

[0015] R⁵ and R⁶ are identical or different, and are one of a halogenatom, a C₁-C₁₀ alkyl group which may be halogenated, a C₆-C₁₀ aryl groupwhich may be halogenated, a C₂-C₁₀ alkenyl group, a C₇-C₄₀-arylalkylgroup, a C₇-C₄₀ alkylaryl group, a C₈-C₄₀ arylalkenyl group, a —NR₂ ¹⁵,—SR¹⁵, —OR¹⁵, —OSiR₃ ¹⁵ or —PR₂ ¹⁵ radical, wherein R¹⁵ is one of ahalogen atom, a C₁-C₁₀ alkyl group, or a C₆-C₁₀ aryl group;

[0016] R⁷ is

[0017] —B(R¹¹)—, ⁻Al(R¹¹)—, —Ge—, —Sn—, —O—, —S—, —SO—, —SO₂—, —N(R¹¹)—,—CO—, —P(R¹¹)—, or —P(O)(R¹¹)—;;

[0018] wherein:

[0019] R¹¹, R¹² and R¹³ are identical or different and are a hydrogenatom, a halogen atom, a C₁-C₂₀ alkyl group, a C₁-C₂₀ fluoroalkyl group,a C₆-C₃₀ aryl group, a C₆-C₃₀ fluoroaryl group, a C₁-C₂₀ alkoxy group, aC₂-C₂₀ alkenyl group, a C₇-C₄₀ arylalkyl group, a C₈-C₄₀ arylalkenylgroup, a C₇-C₄₀ alkylaryl group, or R¹¹ and R¹², or R¹¹ and R¹³,together with the atoms binding them, can form ring systems;

[0020] M² is silicon, germanium or tin;

[0021] R⁸ and R⁹ are identical or different and have the meanings statedfor R¹¹;

[0022] m and n are identical or different and are zero, 1 or 2, m plus nbeing zero, 1 or 2; and

[0023] the radicals R¹⁰ are identical or different and have the meaningsstated for R¹¹, R¹² and R¹³ and two adjacent R¹⁰ radicals can be joinedtogether to form a ring system.

[0024] In yet another embodiment, the invention provides for acrystalline propylene polymer composition comprising:

[0025] (a) from 10 to 90 weight percent of a isotactic crystallinepropylene homopolymer composition comprising a first propylenehomopolymer and a second propylene homopolymer, the isotacticcrystalline propylene homopolymer composition having a molecular weightdistribution of less than 3.0; and

[0026] (b) from 90 to 10 weight percent of a crystalline propylenecopolymer composition comprising a first propylene copolymer and asecond propylene copolymer, the first propylene copolymer and secondpropylene copolymer comprising from 0.05 to 15 weight percent (based onthe total weight of the crystalline propylene polymer composition) of acomonomer, the crystalline propylene copolymer composition having amolecular weight distribution of less than 3.0;

[0027] wherein the crystalline propylene polymer composition has amolecular weight distribution (Mw/Mn) in the range of from 2.1 to 10;and

[0028] wherein the isotactic crystalline propylene homopolymercomposition and crystalline propylene copolymer composition are obtainedin separate stages using a single metallocene catalyst system comprisingtwo different metallocene catalyst components.

[0029] In another embodiment, the invention provides for a process forpreparing a crystalline propylene polymer composition comprising thesteps of:

[0030] (a) polymerizing propylene in a first stage;

[0031] (b) copolymerizing propylene and a comonomer in a second stage;and

[0032] (c) recovering the crystalline propylene polymer compositioncomprising from 0.05 to 15 weight percent of a comonomer (based on thetotal weight of the crystalline propylene polymer composition);

[0033] wherein the steps (a) and (b) are conducted in the presence of asingle metallocene catalyst system comprising two different metallocenecatalyst components.

[0034] The invention also provides for a film comprising a crystallinepropylene polymer composition comprising:

[0035] a) from 10 to 90 weight percent of a crystalline, isotacticpropylene homopolymer composition comprising a first propylenehomopolymer and a second propylene homopolymer; and

[0036] b) from 90 to 10 weight percent of a crystalline propylenecopolymer composition comprising a first propylene copolymer and asecond propylene copolymer, the first propylene copolymer and secondpropylene copolymer comprising from 0.05 to 15 weight percent (based onthe total weight of the crystalline propylene polymer composition) of acomonomer;

[0037] wherein the crystalline propylene polymer composition is preparedusing a single metallocene catalyst system comprising two differentmetallocene catalyst components; and

[0038] wherein the crystalline propylene polymer composition has amolecular weight distribution from 2.1 to 10.

[0039] In another embodiment, the invention provides for a filmcomprising a crystalline propylene polymer composition comprising:

[0040] a) from 10 to 90 weight percent of a crystalline, isotacticpropylene homopolymer composition comprising a first propylenehomopolymer and a second propylene homopolymer, the crystalline,isotactic propylene homopolymer composition having a molecular weightdistribution of less than 3; and

[0041] b) from 90 to 10 weight percent of a crystalline propylenecopolymer composition comprising a first propylene copolymer and asecond propylene copolymer, the crystalline propylene copolymercomposition having a molecular weight distribution of less than 3, thefirst propylene copolymer and the second propylene copolymer comprisingfrom 0.05 to 15 weight percent (based on the total weight of thecrystalline propylene polymer composition) of a comonomer;

[0042] wherein the crystalline propylene polymer composition has amolecular weight distribution in the range of from 2.1 to 10.

DETAILED DESCRIPTION

[0043] This invention relates to (1) methods for making crystallinepropylene polymers; (2) the crystalline propylene polymer compositions;and (3) oriented films made from the crystalline propylene polymercompositions. These are described in turn below.

[0044] As used herein “crystalline” is defined as having identifiablepeak melting points above about 100° C. as determined by DifferentialScanning Calorimetry (DSC peak melting temperatures).

[0045] As used herein, “isotactic” is defined as having at least 40%isotactic pentads according to analysis by ¹³C-NMR. As used herein,“highly isotactic” is defined as having at least 60% isotactic pentadsaccording to analysis by ¹³C-NMR.

[0046] As used herein, “molecular weight” means weight average molecularweight (Mw) and “molecular weight distribution,” (MWD), means Mw dividedby number average molecular weight (Mn).

[0047] As used herein, unless differentiated, “polymerization” includescopolymerization and terpolymerization, “monomer” includes comonomer andtermonomer, and “polymer” includes copolymer and terpolymer.

[0048] Methods for Making Crystalline Propylene Polymer Compositions

[0049] The methods of this invention involve the use of metallocenecatalyst systems that comprise two metallocenes and an activator.Preferably, these catalyst system components are supported on a supportmaterial.

[0050] Metallocenes

[0051] As used herein “metallocene” refers generally to compoundsrepresented by the formula Cp_(m)MR_(n)X_(q) wherein Cp is acyclopentadienyl ring which may be substituted, or derivative thereofwhich may be substituted, M is a Group 4, 5, or 6 transition metal, forexample titanium, zirconium, hafnium, vanadium, niobium, tantalum,chromium, molybdenum and tungsten, R is a hydrocarbyl group orhydrocarboxy group having from one to 20 carbon atoms, X is a halogen,and m=1-3, n=0-3, q=0-3, and the sum of m+n+q is equal to the oxidationstate of the transition metal.

[0052] Methods for making and using metallocenes are very well known inthe art. For example, metallocenes are detailed in U.S. Pat. Nos.4,530,914; 4,542,199; 4,769,910; 4,808,561; 4,871,705; 4,933,403;4,937,299; 5,017,714; 5,026,798; 5,057,475; 5,120,867; 5,278,119;5,304,614; 5,324,800; 5,350,723; and 5,391,790 each fully incorporatedherein by reference.

[0053] Preferred metallocenes are those represented by the formula:

[0054] wherein M is a metal of Group 4, 5, or 6 of the Periodic Tablepreferably, zirconium, hafnium and titanium, most preferably zirconium;

[0055] R¹ and R² are identical or different, preferably identical, andare one of a hydrogen atom, a C₁-C₁₀ alkyl group, preferably a C₁-C₃alkyl group, a C₁-C₁₀ alkoxy group, preferably a C₁-C₃ alkoxy group, aC₆-C₁₀ aryl group, preferably a C₆-C₈ aryl group, a C₆-C₁₀ aryloxygroup, preferably a C₆-C₈ aryloxy group, a C₂-C₁₀ alkenyl group,preferably a C₂-C₄ alkenyl group, a C₇-C₄₀ arylalkyl group, preferably aC₇-C₁₀ arylalkyl group, a C₇-C₄₀ alkylaryl group, preferably a C₇-C₁₂alkylaryl group, a C₉-C₄₀ arylalkenyl group, preferably a C₈-C₁₂arylalkenyl group, or a halogen atom, preferably chlorine;

[0056] R³ and R⁴ are hydrogen atoms;

[0057] R⁵ and R⁶ are identical or different, preferably identical, areone of a halogen atom, preferably a fluorine, chlorine or bromine atom,a C₁-C₁₀ alkyl group, preferably a C₁-C₄ alkyl group, which may behalogenated, a C₆-C₁₀ aryl group, which may be halogenated, preferably aC₆-C₈ aryl group, a C₂-C₁₀ alkenyl group, preferably a C₂-C₄ alkenylgroup, a C₇-C₄₀-arylalkyl group, preferably a C₇-C₁₀ arylalkyl group, aC₇-C₄₀ alkylaryl group, preferably a C₇-C₁₂ alkylaryl group, a C₈-C₄₀arylalkenyl group, preferably a C₈-C₁₂ arylalkenyl group, a —NR₂ ¹⁵,—SR¹⁵, —OR¹⁵, —OSiR₃ ¹⁵ or —PR₂ ¹⁵ radical, wherein R¹⁵ is one of ahalogen atom, preferably a chlorine atom, a C₁-C₁₀ alkyl group,preferably a C₁-C₃ alkyl group, or a C₆-C₁₀ aryl group, preferably aC₆-C₉ aryl group;

[0058] —B(R¹¹)—, ⁻Al(R¹¹)—, —Ge—, —Sn—, —O—, —S—, —SO—, —SO₂—, —N(R¹¹)—,—CO—, —P(R¹¹)—, or —P(O)(R¹¹)—;

[0059] wherein:

[0060] R¹¹, R¹² and R¹³ are identical or different and are a hydrogenatom, a halogen atom, a C₁-C₂₀ alkyl group, preferably a C₁-C₁₀ alkylgroup, a C₁-C₂₀ fluoroalkyl group, preferably a C₁-C₁₀ fluoroalkylgroup, a C₆-C₃₀ aryl group, preferably a C₆-C₂₀ aryl group, a C₆-C₃₀fluoroaryl group, preferably a C₆-C₂₀ fluoroaryl group, a C₁-C₂₀ alkoxygroup, preferably a C₁-C₁₀ alkoxy group, a C₂-C₂₀ alkenyl group,preferably a C₂-C₁₀ alkenyl group, a C₇-C₄₀ arylalkyl group, preferablya C₇-C₂₀ arylalkyl group, a C₉-C₄₀ arylalkenyl group, preferably aC₉-C₂₂ arylalkenyl group, a C₇-C₄₀ alkylaryl group, preferably a C₇-C₂₀alkylaryl group or R¹¹ and R¹², or R¹¹ and R¹³, together with the atomsbinding them, can form ring systems;

[0061] M² is silicon, germanium or tin, preferably silicon or germanium,most preferably silicon;

[0062] R⁸ and R⁹ are identical or different and have the meanings statedfor R¹¹;

[0063] m and n are identical or different and are zero, 1 or 2,preferably zero or 1, m plus n being zero, 1 or 2, preferably zero or 1;and

[0064] the radicals R¹⁰ are identical or different and have the meaningsstated for R¹¹, R¹² and R¹³. Two adjacent R¹⁰ radicals can be joinedtogether to form a ring system, preferably a ring system containing fromabout 4-6 carbon atoms.

[0065] Alkyl refers to straight or branched chain substituents. Halogen(halogenated) refers to fluorine, chlorine, bromine or iodine atoms,preferably fluorine or chlorine.

[0066] Particularly preferred metallocenes are compounds of thestructures (A) and (B):

[0067] wherein:

[0068] M¹ is Zr or Hf, R¹ and R² are methyl or chlorine, and R⁵, R⁶ R⁸,R⁹, R¹⁰, R¹¹ and R¹² have the above-mentioned meanings.

[0069] These chiral metallocenes may be used as a racemate for thepreparation of highly isotactic polypropylene copolymers. It is alsopossible to use the pure R or S form. An optically active polymer can beprepared with these pure stereoisomeric forms. Preferably the meso formof the metallocene is removed to ensure the center (i.e., the metalatom) provides stereoregular polymerization. Separation of thestereoisomers can be accomplished by known literature techniques. Forspecial products it is also possible to use rac/meso mixtures.

[0070] Generally, these metallocenes are prepared by a multi-stepprocess involving repeated deprotonations/metallations of the aromaticligands and introduction of the bridge and the central atom by theirhalogen derivatives. The following reaction scheme illustrates thisgeneric approach:

[0071] Additional methods for preparing metallocenes are fully describedin the Journal of Organometallic Chem., volume 288, (1985), pages 63-67,and in EP-A-320762, both of which are herein fully incorporated byreference.

[0072] Illustrative but non-limiting examples of preferred metallocenesinclude:

[0073] Dimethylsilandiylbis (2-methyl-4-phenyl-1-indenyl)ZrCl₂

[0074] Dimethylsilandiylbis(2-methyl-4,5-benzoindenyl)ZrCl₂;

[0075] Dimethylsilandiylbis(2-methyl-4,6-diisopropylindenyl)ZrCl₂;

[0076] Dimethylsilandiylbis(2-ethyl-4-phenyl-1-indenyl)ZrCl₂;

[0077] Dimethylsilandiylbis (2-ethyl-4-naphthyl-1-indenyl)ZrCl₂,

[0078] Phenyl(methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)ZrCl₂,

[0079] Dimethylsilandiylbis(2-methyl-4-(1-naphthyl)-1-indenyl)ZrCl₂,

[0080] Dimethylsilandiylbis(2-methyl-4-(2-naphthyl)-1-indenyl)ZrCl₂,

[0081] Dimethylsilandiylbis(2-methyl-indenyl)ZrCl₂,

[0082] Dimethylsilandiylbis(2-methyl-4,5-diisopropyl-1-indenyl)ZrCl₂,

[0083] Dimethylsilandiylbis(2,4,6-trimethyl-1-indenyl)ZrCl₂,

[0084]Phenyl(methyl)silandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl₂,

[0085] 1,2-Ethandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl₂,

[0086] 1,2-Butandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl₂,

[0087] Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)ZrCl₂,

[0088] Dimethylsilandiylbis(2-methyl-4-isopropyl-1-indenyl)ZrCl₂,

[0089] Dimethylsilandiylbis(2-methyl-4-t-butyl-1-indenyl)ZrCl₂,

[0090] Phenyl(methyl)silandiylbis(2-methyl-4-isopropyl-1-indenyl)ZrCl₂,

[0091] Dimethylsilandiylbis(2-ethyl-4-methyl-1-indenyl)ZrCl₂,

[0092] Dimethylsilandiylbis(2,4-dimethyl-1-indenyl)ZrCl₂,

[0093] Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)ZrCl₂,

[0094] Dimethylsilandiylbis(2-methyl-α-acenaphth-1-indenyl)ZrCl₂,

[0095] Phenyl(methyl)silandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,

[0096]Phenyl(methyl)silandiylbis(2-methyl-4,5-(methylbenzo)-1-indenyl)ZrCl₂,

[0097]Phenyl(methyl)silandiylbis(2-methyl-4,5-(tetramethylbenzo)-1-indenyl)ZrCl₂,

[0098] Phenyl(methyl)silandiylbis (2-methyl-a-acenaphth-1-indenyl)ZrCl₂,

[0099] 1,2-Ethandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,

[0100] 1,2-Butandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,

[0101] Dimethylsilandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,

[0102] 1,2-Ethandiylbis(2,4,7-trimethyl-1-indenyl)ZrCl₂,

[0103] Dimethylsilandiylbis(2-methyl-1-indenyl)ZrCl₂,

[0104] 1,2-Ethandiylbis(2-methyl-1-indenyl)ZrCl₂,

[0105] Phenyl(methyl)silandiylbis(2-methyl-1-indenyl)ZrCl₂,

[0106] Diphenylsilandiylbis(2-methyl-1-indenyl)ZrCl₂,

[0107] 1,2-Butandiylbis(2-methyl-1-indenyl)ZrCl₂,

[0108] Dimethylsilandiylbis(2-ethyl-1-indenyl)ZrCl₂,

[0109] Dimethylsilandiylbis(2-methyl-5-isobutyl-1-indenyl)ZrCl₂,

[0110] Phenyl(methyl)silandiylbis(2-methyl-5-isobutyl-1-indenyl)ZrCl₂,

[0111] Dimethylsilandiylbis(2-methyl-5-t-butyl-1-indenyl)ZrCl₂,

[0112] Dimethylsilandiylbis(2,5,6-trimethyl-1-indenyl)ZrCl₂, and thelike.

[0113] These preferred metallocene catalyst components are described indetail in U.S. Pat. Nos. 5,145,819; 5,243,001; 5,239,022; 5,329,033;5,296,434; 5,276,208; and 5,374,752; and EP 549 900 and 576 970 all ofwhich are herein fully incorporated by reference.

[0114] The metallocenes preferably selected for use in this inventionare two or more different metallocenes which, when used alone, produceisotactic, crystalline propylene polymer and when used in combination,produce polymer having the attributes desired for the particular filmapplication of interest. Particularly preferred metallocenes are thoseselected from formulas A and/or B which when used alone to producepropylene homopolymer, are capable of producing an isotactic polymerhaving a weight average molecular weight of from about 25,000 to about1,500,000 at commercially attractive temperatures of from about 50° C.to about 120° C. Preferably two or more metallocenes are selected whichproduce polymers having different molecular weights. This results in abroader molecular weight distribution.

[0115] The metallocenes used may show different molecular weightresponses when in the presence of comonomer as will be described laterin the Examples. This will also affect the molecular weight distributionof the product. For example, we have found that the incorporation of ≦1wt % ethylene comonomer during the polymerization process as describedherein results in a substantial broadening of the molecular weightdistribution at the high molecular weight end. This is unexpected sincewith both the individual metallocenes used, the molecular weight dropswith ethylene addition.

[0116] Additional broadening of molecular weight distribution may bepracticed through reactor process techniques. For example, operating thedifferent stages of a multiple stage polymerization process with varyinglevels of hydrogen, a molecular weight regulator, is known in the art toproduce broadening of molecular weight distribution.

[0117] Preferably the catalyst system used in the process of thisinvention comprises one metallocene of the formula A and/or B above thatis capable of producing propylene homopolymer at polymerizationtemperatures of from about 50° C. to about 100° C. having a molecularweight in the range of from about 25,000 to about 300,000, preferablyfrom about 100,000 to about 300,000. The other metallocene is preferablycapable of producing propylene homopolymer at the same temperature thathas a molecular weight in the range of from about 300,000 to about1,500,000, preferably from about 300,000 to about 1,000,000. Preferably,each metallocene produces a polymer component having a molecular weightdistribution of less than about 3, preferably less than about 2.5.

[0118] Thus preferably one metallocene is selected from the groupconsisting of rac-: dimethylsilandiylbis(2-methylindenyl)zirconiumdichloride; dimethylsilandiylbis(2,4-dimethylindenyl)zirconiumdichloride; dimethylsilandiylbis(2,5,6-trimethylindenyl)zirconiumdichloride; dimethylsilandiylbis indenyl zirconium dichloride;dimethylsilandiylbis(4,5,6,7-tetrahydroindenyl)zirconium dichloride anddimethylsilandiylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride.

[0119] Preferably the other metallocene is selected from the groupconsisting of rac-:dimethylsilandiylbis(2-methyl-4-phenylindenyl)zirconium dichloride;dimethylsilandiylbis(2-methyl-4,6-diisopropylindenyl)zirconiumdichloride; dimethylsilandiylbis(2-methyl-4-napthylindenyl)zirconiumdichloride; and dimethylsilandiylbis(2-ethyl-4-phenylindenyl)zirconiumdichloride.

[0120] The ratio of metallocenes used in polymerization will dependpartly on the activities of the metallocenes and on the desiredcontribution of each. Thus, for example, if two metallocenes are used ina 1:1 ratio and the activities of each are similar, then the polymerproduct will be expected to comprise about 50% of polymer produced byone metallocene and about 50% of polymer produced by the other. Thebreadth of the product's molecular weight distribution will depend atleast partly on the difference in molecular weight capability betweenthe metallocenes. The addition of comonomer and/or hydrogen in thepolymerization process may affect the contribution of each metalloceneas described in detail below.

[0121] In an alternative embodiment, a different set of metallocenes isused in each stage of polymerization.

[0122] Activators

[0123] Metallocenes are generally used in combination with some form ofactivator in order to create an active catalyst system. The term“activator” is defined herein to be any compound or component, orcombination of compounds or components, capable of enhancing the abilityof one or more metallocenes to polymerize olefins to polyolefins.Alklyalumoxanes are preferably used as activators, most preferablymethylalumoxane (MAO). Generally, the alkylalumoxanes preferred for usein olefin polymerization contain about 5 to 40 of the repeating units:

[0124] for linear species and

[0125] for cyclic species

[0126] where R is a C₁-C₈ alkyl including mixed alkyls. Particularlypreferred are the compounds in which R is methyl. Alumoxane solutions,particularly methylalumoxane solutions, may be obtained from commercialvendors as solutions having various concentrations. There are a varietyof methods for preparing alumoxane, non-limiting examples of which aredescribed in U.S. Pat. Nos. 4,665,208, 4,952,540, 5,091,352, 5,206,199,5,204,419, 4,874,734, 4,924,018, 4,908,463, 4,968,827, 5,308,815,5,329,032, 5,248,801, 5,235,081, 5,157,137, 5,103,031 and EP-A-0 561476, EP-B1-0 279 586, EP-A-0 594-218 and WO 94/10180, each fullyincorporated herein by reference. (as used herein unless otherwisestated “solution” refers to any mixture including suspensions.)

[0127] Some MAO solutions tend to become cloudy and gelatinous overtime. It may be advantageous to clarify such solutions prior to use. Anumber of methods are used to create gel-free MAO solutions or to removegels from the solutions. Gelled solutions are often simply filtered ordecanted to separate the gels from the clear MAO. U.S. Pat. No.5,157,137, for example, discloses a process for forming clear, gel-freesolutions of alkylalumoxane by treating a solution of alkylalumoxanewith an anhydrous salt and/or hydride of an alkali or alkaline earthmetal.

[0128] Ionizing activators may also be used to activate metallocenes.These activators are neutral or ionic, or are compounds such astri(n-butyl)ammonium tetrakis(pentafluorophenyl)boron, which ionize theneutral metallocene compound. Such ionizing compounds may contain anactive proton, or some other cation associated with but not coordinatedor only loosely coordinated to the remaining ion of the ionizingcompound. Combinations of activators may also be used, for example,alumoxane and ionizing activators in combinations, see for example, WO94/07928.

[0129] Descriptions of ionic catalysts for coordination polymerizationcomprised of metallocene cations activated by non-coordinating anionsappear in the early work in EP-A-0 277 003, EP-A-0 277 004 and U.S. Pat.No. 5,198,401 and WO-A-92/00333 (incorporated herein by reference).These teach a preferred method of preparation wherein metallocenes(bisCp and monoCp) are protonated by an anion precursor such that analkyl/hydride group is abstracted from a transition metal to make itboth cationic and charge-balanced by the non-coordinating anion.

[0130] The term “noncoordinating anion” means an anion which either doesnot coordinate to said cation or which is only weakly coordinated tosaid cation thereby remaining sufficiently labile to be displaced by aneutral Lewis base. “Compatible” noncoordinating anions are those whichare not degraded to neutrality when the initially formed complexdecomposes. Further, the anion will not transfer an anionic substituentor fragment to the cation so as to cause it to form a neutral fourcoordinate metallocene compound and a neutral by-product from the anion.Noncoordinating anions useful in accordance with this invention arethose which are compatible, stabilize the metallocene cation in thesense of balancing its ionic charge in a +1 state, yet retain sufficientlability to permit displacement by an ethylenically or acetylenicallyunsaturated monomer during polymerization.

[0131] The use of ionizing ionic compounds not containing an activeproton but capable of producing both the active metallocene cation and anoncoordinating anion is also known. See, EP-A-0 426 637 and EP-A-0 573403 (incorporated herein by reference). An additional method of makingthe ionic catalysts uses ionizing anion pre-cursors which are initiallyneutral Lewis acids but form the cation and anion upon ionizing reactionwith the metallocene compounds, for example the use oftris(pentafluorophenyl) boron. See EP-A-0 520 732 (incorporated hereinby reference). Ionic catalysts for addition polymerization can also beprepared by oxidation of the metal centers of transition metal compoundsby anion pre-cursors containing metallic oxidizing groups along with theanion groups, see EP-A-0 495 375 (incorporated herein by reference).

[0132] Where the metal ligands include halogen moieties (for example,bis-cyclopentadienyl zirconium dichloride) which are not capable ofionizing abstraction under standard conditions, they can be convertedvia known alkylation reactions with organometallic compounds such aslithium or aluminum hydrides or alkyls, alkylalumoxanes, Grignardreagents, etc. See EP-A-0 500 944 and EP-A1-0 570 982 (incorporatedherein by reference) for in situ processes describing the reaction ofalkyl aluminum compounds with dihalo-substituted metallocene compoundsprior to or with the addition of activating anionic compounds.

[0133] Support Materials

[0134] The catalyst systems used in the process of this invention arepreferably supported using a porous particulate material, such as forexample, talc, inorganic oxides, inorganic chlorides and resinousmaterials such as polyolefin or polymeric compounds.

[0135] The most preferred support materials are porous inorganic oxidematerials, which include those from the Periodic Table of Elements ofGroups 2, 3, 4, 5, 13 or 14 metal oxides. Silica, alumina,silica-alumina, and mixtures thereof are particularly preferred. Otherinorganic oxides that may be employed either alone or in combinationwith the silica, alumina or silica-alumina are magnesia, titania,zirconia, and the like.

[0136] Preferably the support material is porous silica which has asurface area in the range of from about 10 to about 700 m²/g, a totalpore volume in the range of from about 0.1 to about 4.0 cc/g and anaverage particle size in the range of from about 10 to about 500 μm.More preferably, the surface area is in the range of from about 50 toabout 500 m²/g, the pore volume is in the range of from about 0.5 toabout 3.5 cc/g and the average particle size is in the range of fromabout 20 to about 200 μm. Most preferably the surface area is in therange of from about 100 to about 400 m²/g, the pore volume is in therange of from about 0.8 to about 3.0 cc/g and the average particle sizeis in the range of from about 30 to about 100 μm. The average pore sizeof typical porous support materials is in the range of from about 10 toabout 1000 Å. Preferably, a support material is used that has an averagepore diameter of from about 50 to about 500 Å, and most preferably fromabout 75 to about 350 Å. It may be particularly desirable to dehydratethe silica at a temperature of from about 100° C. to about 800° C.anywhere from about 3 to about 24 hours.

[0137] The metallocenes, activator and support material may be combinedin any number of ways. Suitable support techniques are described in U.S.Pat. Nos. 4,808,561 and 4,701,432 (each fully incorporated herein byreference.). Preferably the metallocenes and activator are combined andtheir reaction product supported on the porous support material asdescribed in U.S. Pat. No. 5,240,894 and WO 94/28034, WO 96/00243, andWO 96/00245 (each fully incorporated herein by reference.)Alternatively, the metallocenes may be preactivated separately and thencombined with the support material either separately or together. If themetallocenes are separately supported, then preferably, they are driedthen combined as a powder before use in polymerization.

[0138] Regardless of whether the metallocenes and their activator areseparately precontacted or whether the metallocenes and activator arecombined at once, the total volume of reaction solution applied toporous support is preferably less than about 4 times the total porevolume of the porous support, more preferably less than about 3 timesthe total pore volume of the porous support and even more preferably inthe range of from more than about 1 to less than about 2.5 times thetotal pore volume of the porous support. Procedures for measuring thetotal pore volume of porous support are well known in the art. Thepreferred method is described in Volume 1, Experimental Methods inCatalyst Research, Academic Press, 1968, pages 67-96.

[0139] Methods of supporting ionic catalysts comprising metallocenecations and noncoordinating anions are described in WO 91/09882, WO94/03506, WO 96/04319 and in co-pending U.S. Ser. No. 08/248,284, filedAug. 3, 1994 (incorporated herein by reference). The methods generallycomprise either physical adsorption on traditional polymeric orinorganic supports that have been largely dehydrated and dehydroxylated,or using neutral anion precursors that are sufficiently strong Lewisacids to activate retained hydroxy groups in silica containing inorganicoxide supports such that the Lewis acid becomes covalently bound and thehydrogen of the hydroxy group is available to protonate the metallocenecompounds.

[0140] The supported catalyst system may be used directly inpolymerization or the catalyst system may be prepolymerized usingmethods well known in the art. For details regarding prepolymerization,see U.S. Pat. Nos. 4,923,833 and 4,921,825, EP 0 279 863 and EP 0 354893 each of which is fully incorporated herein by reference.

[0141] Polymerization Processes

[0142] The polymer compositions of this invention are generally preparedin a multiple stage process wherein homopolymerization andcopolymerization are conducted separately in parallel or, preferably inseries. In a preferred mode, propylene is homopolymerized and thereafterpropylene and comonomer are copolymerized in the presence of theinitially produced homopolymer using the above described metallocenecatalyst systems. If, however, the copolymer is prepared first, thesubsequently prepared “homopolymer” is likely to contain some traces ofcomonomer.

[0143] Individually, each stage may involve any process including gas,slurry or solution phase or high pressure autoclave processes.Preferably a slurry (bulk liquid propylene) polymerization process isused in each stage.

[0144] A slurry polymerization process generally uses pressures in therange of from about 1 to about 100 atmospheres (about 0.1 to about 10MPa) or even greater and temperatures in the range of from −60° C. toabout 150° C. In a slurry polymerization, a suspension of solid,particulate polymer is formed in a liquid or supercriticalpolymerization medium to which propylene and comonomers and oftenhydrogen along with catalyst are added. The liquid employed in thepolymerization medium can be, for example, an alkane or a cycloalkane.The medium employed should be liquid under the conditions ofpolymerization and relatively inert such as hexane and isobutane. In thepreferred embodiment, propylene serves as the polymerization diluent andthe polymerization is carried out using a pressure of from about 200 kPato about 7,000 kPa at a temperature in the range of from about 50° C. toabout 120° C.

[0145] The periods of time for each stage will depend upon the catalystsystem, comonomer and reaction conditions. In general, propylene shouldbe homopolymerized for a time period sufficient to yield a compositionhaving from about 10 to about 90 weight percent homopolymer based on thetotal weight of the polymer, preferably from about 20 to about 80 weightpercent, even more preferably from about 30 to about 70 homopolymerweight percent based on the total weight of the polymer.

[0146] The polymerization may be conducted in batch or continuous modeand the entire polymerization may take place in one reactor or,preferably, the polymerization may be carried out in a series ofreactors. If reactors in series are used, then the comonomer may beadded to any reactor in the series, however, preferably, the comonomeris added to the second or subsequent reactor.

[0147] Hydrogen may be added to the polymerization system as a molecularweight regulator in the first and/or subsequent reactors depending uponthe particular properties of the product desired and the specificmetallocenes used. When metallocenes having different hydrogen responsesare used, the addition of hydrogen will affect the molecular weightdistribution of the polymer product accordingly. A preferred productform is to have the comonomer be present in the high molecular weightspecies of the total polymer composition to provide a favorable balanceof good film stretchability without breaking, coupled with lowextractables, low haze and good moisture barrier in the film.Accordingly in this preferred case, the same or lower levels of hydrogenare utilized during copolymerization as were used during polymerizationin the second or subsequent reactor.

[0148] Polymer Compositions

[0149] The polymer compositions of this invention are a reactor blend ofcrystalline propylene homopolymer and copolymer. The polymer comprisesfrom about 10 to about 90 weight percent homopolymer based on the totalweight of the polymer, preferably from about 20 to about 80 weightpercent, even more preferably from about 30 to about 70 weight percenthomopolymer based on the total weight of the polymer.

[0150] As shown later in the Examples, a reactor blend of justcrystalline propylene homopolymers made in the different polymerizationstages, using a system of mixed metallocene catalysts, does provide anenhancement in film orientability and good film properties over the caseof a propylene homopolymer made via a single metallocene catalyst. Thehomopolymer/copolymer compositions of the invention however, provide afavorable balance of broad film processability range and properties.

[0151] Any comonomer may be used to make the polymers of this invention.Preferably the comonomer is selected from the alpha-olefin groupconsisting of ethylene, 1-butene, 1-pentene, 1-hexene, and 1-octene.Combinations of comonomers and substituted comonomers such as4-methylpentene-1 can also be used. The most preferred of thesecomonomers are ethylene, 1-pentene, and 1-hexene. Diolefins and cyclicolefins may also be used.

[0152] The amount of comonomer used will depend on the type of comonomerand desired properties. The final composition may contain any amount ofcomonomer as long as the components of the composition remaincrystalline. In general the amount of comonomer units based on the totalweight of the polymer is in the range of from about 0.05 to about 15weight percent, preferably from about 0.1 to about 10 weight percent,even more preferably from about 0.5 to about 8 weight percent, and mostpreferably from about 0.5 to about 5 weight percent based on the totalweight of the polymer. Conversely, the polymer comprises from about99.95 to about 85 weight percent propylene units based on the totalweight of the polymer, preferably from about 99.90 to about 90 weightpercent, even more preferably from about 99.5 to about 92 weightpercent, and most preferably from about 99.5 to about 95 weight percentpropylene units based on the total weight of the polymer.

[0153] A desirable feature of this composition is the presence ofcomonomer in the high molecular weight species, to selectively reducethe crystallinity and improve film orientability at stretchingtemperatures, while the homopolymer, higher crystalline componentprovides the desirable film properties such as stiffness and barrier.The polymers of this invention also retain the low extractables levelscharacteristic of single-site metallocene-based polymers, which aretypically under 2 weight percent, as measured by 21 CFR177.1520(d)(3)(ii). As will be shown later in the Examples, the polymersof this invention combine the stiffness and barrier properties ofhomopolypropylene with the enhanced low temperature stretchability,without breaks, of a random copolymer.

[0154] The propylene polymer compositions of this invention areparticularly suitable for oriented film applications and preferably havea weight average molecular weight (MW) that is in the range of fromabout 140,000 to about 750,000 preferably from about 150,000 to about500,000, and most preferably from about 200,000 to about 400,000. Thesepolymer compositions preferably have a melt flow rate (MFR) that is inthe range of from about 0.2 dg/min. to about 30 dg/min., preferably fromabout 0.5 dg/min. to about 20 dg/min., even more preferably from about 1dg/min. to about 10 dg/min. The polymer compositions of this inventionhave a broadened molecular weight distribution as compared to polymersprepared with only one type of metallocene catalyst. Preferably thepolymers have a molecular weight distribution (M_(w)/M_(n)) in the rangeof from about 2.1 to about 10.0; more preferably from about 2.5 to about7.0.

[0155] The polymer compositions of this invention will have a tailoredcomposition distribution reflecting their homopolymer/copolymer makeupand the presence of the component contributions from each of themetallocenes used. The copolymer species derived from each metallocenewill be narrow in composition distribution, typical for single sitemetallocene-based polymers. The final composition distribution willdepend on the level of comonomer, the ratio of homopolymer to copolymerproduced and the comonomer incorporating tendencies of the individualmetallocenes. The design of the molecular weight distribution, tacticitydistribution, and composition distribution of the final compositiondepends on the requirements of the targeted end application.

[0156] The polymers of this invention can be blended with otherpolymers, particularly with other polyolefins. Examples of such would beblends with conventional propylene polymers.

[0157] Oriented Films

[0158] The crystalline propylene polymers of this invention exhibitexceptional film orientability and the films exhibit a good balance ofproperties. Any film fabrication method may be used to prepare theoriented films of this invention as long as the film is oriented atleast once in at least one direction. Typically, commercially desirableoriented polypropylene films are biaxially oriented sequentially orsimultaneously. The most common practice is to orient the film firstlongitudinally and then in the transverse direction. Two well knownoriented film fabrication processes include the tenter frame process andthe double bubble process.

[0159] We have found that the novel structure of the crystallinepropylene compositions of this invention translates to distinctdifferences versus standard films made with today's Ziegler-Nattaproduced propylene polymers and compared with films produced with asingle metallocene. As discussed in more detail below, biaxialstretching studies show that the films of this invention have asubstantially broader processability range and can be evenly stretchedat lower temperature. Stretching studies at elevated temperatures oncast sheets along machine direction (MD) and transverse direction (TD)indicate that the films of this invention stretch easily withoutbreaking at lower stretching temperatures when compared to Ziegler-Nattaproduced propylene polymers. This indicates a capability to operate atsignificantly higher line speeds on commercial tenter frame lines, whilestill making oriented films having good clarity, stiffness and barrierproperties.

[0160] The final films of this invention may generally be of anythickness, however, preferably the thickness is in the range of fromabout 1-200 μm, preferably 2-150 μm, and more preferably, 5 to 75 μm.There is no particular restriction with respect to draw ratio on filmstretching, however, preferably the draw ratio is from about 4 to about10 fold for monoaxially oriented films and from about 4 to about 15 foldin the transverse direction in the case of biaxially oriented films.Longitudinal (MD) and transverse stretching is preferably carried out ata temperature in the range of from about 70° C. to about 200° C.,preferably from about 80° C. to about 190° C. The films may becoextruded or laminated and/or may be single or multi layered with thefilm of the invention comprising at least one component of the layers,typically the core layer.

[0161] Additives may be included in the film polymer compositions ofthis invention. Such additives and their use are generally well known inthe art. These include those commonly employed with plastics such asheat stabilizers or antioxidants, neutralizers, slip agents, antiblockagents, pigments, antifogging agents, antistatic agents, clarifiers,nucleating agents, ultraviolet absorbers or light stabilizers, fillersand other additives in conventional amounts. Effective levels are knownin the art and depend on the details of the base polymers, thefabrication mode and the end application. In addition, hydrogenatedand/or petroleum hydrocarbon resins may be used as additives.

[0162] The film surfaces may be treated by any of the known methods suchas corona or flame treatment. In addition standard film processing (e.g.annealing) and converting operations may be adopted to transform thefilm at the line into usable products.

EXAMPLES

[0163] Samples 1, 2A and 2B are propylene polymers consistent with thisinvention. These were compared against several metallocene-based andconventional Ziegler-Natta based propylene polymers as follows. Sample 3was prepared from the same metallocene catalyst system (comprising twometallocenes) used to make Samples 1, 2A and 2B, but without using anycomonomer. Samples 4 and 5 were prepared from a single metallocene-basedcatalyst; Sample 4 is a homopolymer, while Sample 5 contains ethylene ascomonomer. The Ziegler-Natta produced propylene polymers are Samples 6,7, 8 and 9. Samples 6 and 9 are polymers of controlled crystallinity,comprising a reactor blend of propylene homopolymer and propylenecopolymer, similar to the invention polymers but prepared fromconventional Ziegler-Natta catalyst. Product PP4792 E1 is an example ofSample 6. Product PP4782, at a slightly lower MFR (2.1 versus 2.6 forPP4792 E1) is an example of Sample 9. Samples 7 and 8 are conventionalrandom copolymer polypropylenes. Products PP 4822 and PD 9012 E1 areexamples of Samples 7 and 8 respectively. The Ziegler-Natta productsabove (Samples 6, 7, 8 and 9) are available commercially from ExxonChemical Company, Houston Tex., USA. Table 1 provides characterizationdata describing Samples 1 to 9.

[0164] The copolymer, Sample 1, was prepared by using a catalyst systemthat employed an equimolar mix of two metallocenes on a silica support.The catalyst system was prepared as follows. In an inert nitrogenatmosphere, 8.0 g of racdimethylsilanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride wascombined with 6.0 g of dimethylsilanediylbis(2-methyl-indenyl)zirconiumdichloride and 780 g of 30 wt % methylalumoxane solution in toluene(Albemarle Corporation, Baton Rouge, La.). 860 g of toluene was added todilute the solution. Separately 939 g MS948 silica (1.6 cc/g porevolume—available from Davison Chemical Division of W. R. Grace,Baltimore, Md.) previously dehydrated to 600° C. in a stream of flowingN₂ was charged to the catalyst preparation vessel. With the agitator onthe metallocene-aluminoxane solution was added to the silica. Afteraddition of the solution mixing continued for one hour and then vacuumwas applied to the vessel. A slight nitrogen purge was added to thebottom of the vessel to aid in removing the volatiles. At the end ofdrying 1454 g of free flowing solid was obtained. Analysis showed aloading of 8.95 wt % Al and 0.17 wt % Zr with an Al/Zr molar ratio of180.

[0165] Several batches of the catalyst system were combined to providesufficient charge for the polymerization run. The catalyst system wasoil slurried (20 parts by weight to 80 parts by weight Drakeol™ 35available from Penreco, Dickinson, Tex.) for ease of addition to thereactor.

[0166] The procedure for polymerizing Sample 1 was as follows. Thepolymerization was conducted in a pilot scale continuous, stirred tank,bulk liquid phase polymerization process employing two reactors inseries. The reactors were equipped with jackets for removing the heat ofpolymerization. The reactor temperature was set at 70° C. in the firstreactor and 64° C. in the second reactor. Catalyst was fed at anestimated rate of 5 g/hr. Triethylaluminum (TEAL) was employed asscavenger and fed at a rate of 160 ml/hr of a 2 wt % solution of TEAL inhexane solvent. Propylene was fed at a rate of about 73 kg/hr to thefirst reactor and about 27.5 kg/hr to the second reactor. Ethylenecomonomer was added only to the second reactor at a feed rate as neededto result in an overall incorporation of about 0.8 wt % ethylene in thefinal polymer. Hydrogen was added for molecular weight control at 500mppm in the first reactor. No addition of fresh hydrogen was fed to thesecond reactor. Residence times were about 2.75 hours in the firstreactor and about 2 hours in the second reactor. The production rate ofpolymer was about 32 kg/hr. The polymer was discharged from the reactorsas a granular product having an MFR of about 2.0 dg/min. and ethylenelevel of about 0.8 wt %. Evaluation of the intermediate product from thefirst reactor showed a homopolypropylene with an MFR of 4.0.

[0167] The copolymer, Sample 2A, was prepared using the same catalystsystem and polymerization procedure as described above for Sample 1. Theonly difference was a slight increase in the ethylene comonomer feed tothe second reactor, resulting in an overall ethylene incorporation inthe final product of about 1.0 wt %. The final granular product had anMFR of about 1.0; that of the intermediate product from the firstreactor about 4.0. Both polymers, Samples 1 and 2A, comprise a reactorblend of a high(er) MFR homopolypropylene with a low MFR randomcopolymer.

[0168] The copolymer, Sample 2B, was prepared using a similar catalystsystem and polymerization procedure as described above for Samples 1 and2A, with some modifications. On catalyst, MS 952 silica (DavisonChemical, Division of W. R. Grace, Baltimore, Md.), previouslydehydrated to 600° C. under N₂ was used instead of MS 948. Also,following the addition of the metallocene/alumoxane mixture to thesilica, a solution containing Kemamine AS-990 (Witco Corporation,Greenwich, Conn.) in toluene (1 wt % of AS-990 based on weight ofsilica) was added to the slurry before drying. On reactorpolymerization, the reactor levels were adjusted to provide a 70%/30%split between product made in the first and second reactors, versus a55%/45% split during the production of Samples 1 and 2A.

[0169] The homopolymer, Sample 3, was also prepared using thetwo-metallocene mix described above. Several batches of the catalystwere combined to provide the charge for the polymerization run. Thecatalyst system was oil slurried (15 wt %) for ease of addition to thereactor.

[0170] The procedure for polymerizing Sample 3 was as follows. Thepolymerization was conducted in a pilot scale continuous, stirred tank,bulk liquid phase polymerization process employing two reactors inseries. The reactors were equipped with jackets for removing the heat ofpolymerization. The reactor temperature was set at 70° C. in the firstreactor and 64° C. in the second reactor. Catalyst was fed at anestimated rate of 13.5 g/hr. Triethylaluminum (TEAL) was employed asscavenger and fed at a rate of 2 ml/min. of a 2 wt % solution of TEAL inhexane solvent. Propylene was fed at a rate of about 65.8 kg/hr to thefirst reactor and about 27.2 kg/hr to the second reactor. Hydrogen wasadded for molecular weight control at 500 mppm in the first reactor and900 mppm in the second reactor. Residence times were about 3 hours inthe first reactor and about 2 hours in the second reactor. Theproduction rate of polymer was about 25 kg/hr. The final polymer wasdischarged from the reactors as a granular homopolymer product having anMFR of 2.0 dg/min.

[0171] The homopolymer, Sample 4, was prepared using the metallocenecatalyst system rac dimethylsilylbis(2-methyl-4-phenylindenyl)zirconiumdichloride, activated with methylalumoxane and supported on silica. Thecatalyst system was prepared in the following manner.

[0172] A precursor solution was prepared by combining 343 g of 30 wt %methylalumoxane in toluene (Albemarle Corp., Baton Rouge, La.)representing 1.76 moles Al with 6.36 g ofdimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride (0.01moles Zr) by stirring. Then 367 g of toluene was added and stirring wascontinued for 15 minutes. The precursor solution (625.9 g) was added to392 g of Davison MS 948 silica (1.6 cc/g pore volume—available from W.R. Grace, Davison Chemical Division, Baltimore, Md.) previously heatedto 600° C. under N₂. The ratio of liquid volume to total silica porevolume was 1.10. The solid had the consistency of damp sand and wasdried at reduced pressure (483+mm Hg vacuum) and temperatures as high as50° C. over 16 hours. 485.5 g finely divided, free-flowing solidcatalyst were obtained. Elemental analysis showed 0.09 wt % Zr and 7.37wt % Al.

[0173] Several batches of catalyst system were combined to provide thecharge for the polymerization run. The catalyst system was oil slurried(Drakeol™, 15 wt %) for ease of addition to the reactor. The procedurefor polymerizing Sample 4 was as follows. The polymerization wasconducted in a pilot scale, two reactor, continuous, stirred tank, bulkliquid-phase process. The reactors were equipped with jackets forremoving the heat of polymerization. The reactor temperature was set at70° C. in the first reactor and 66° C. in the second reactor. Catalystwas fed at a rate of 6.6 g/hr. TEAL (2 wt % in hexane) was used as ascavenger at a rate of 1.6 g/hr. The catalyst system prepared above wasfed as a 15% slurry in mineral oil and was flushed into the reactor withpropylene. Propylene monomer was fed to the first reactor at a rate of73 kg/hr and to the second reactor at a rate of 27 kg/hr. Reactorresidence time was about 2.3 hours in the first reactor and about 1.7hours in the second reactor. Polymer production rates were about 16kg/hr in the first reactor and 8 kg/hr in the second reactor. Polymerwas discharged from the reactors as granular product having a MFR of 4.3dg/min.

[0174] The copolymer, Sample 5, was prepared using the metallocenecatalyst systemrac-dimethylsilanediylbis(2-methyl-4,5-benzo-indenyl)zirconiumdichloride, activated with methylalumoxane and supported on silica. Thecatalyst system was prepared in the following manner.

[0175] A precursor solution was prepared by combining 837.4 g of 30 wt %methylalumoxane in toluene (Albemarle Corp., Baton Rouge, La.)representing 4.31 moles Al with 8.45 g ofdimethylsilanediylbis(2-methyl-4,5-benzo-indenyl)zirconium dichloride(0.015 moles Zr) by stirring. Then 249 g of toluene was added andstirring was continued for 15 minutes. The precursor solution was addedto 783 g of Davison MS948 silica (1.6 cc/g pore volume—available from W.R. Grace, Davison Chemical Division, Baltimore, Md.) previously heatedto 600° C. under N₂. The ratio of liquid volume to total silica porevolume was 0.95. The solid appeared dry and free flowing. The volatileswere removed by drying at reduced pressure (737+mm Hg vacuum) andtemperatures as high as 65° C. over 24.5 hours. 1056 g finely divided,free-flowing solid catalyst were obtained. Elemental analysis showed0.13 wt % Zr and 12.14 wt % Al.

[0176] Several batches of this catalyst system were combined to yieldthe charge required for the polymerization run. Prior to using forpolymerization, 2 wt % Kemamine AS 990 (available from Witco Corp.,Greenwich Conn.), was added to the catalyst dry solids. The catalyst wasthen oil slurried (Drakeol™, 15 wt %) for ease of addition to thereactor.

[0177] The procedure for polymerizing Sample 5 was as follows. Thepolymerization of propylene/ethylene copolymer was conducted in a pilotscale continuous, stirred tank, bulk liquid phase polymerization processemploying two reactors in series. The reactors were equipped withjackets for removing the heat of polymerization. The reactor temperaturewas set at 55° C. in the first reactor and 51° C. in the second reactor.Catalyst was fed at rate of 9.2 g/hr. Triethylaluminum (TEAL) wasemployed as scavenger and fed at a rate of 2.25 ml/min. of a 2 wt %solution of TEAL in hexane solvent. Propylene was fed at a rate of about99.8 kg/hr. Ethylene was used as a comonomer and its flow rate adjustedto provide an incorporation level of about 1.0 wt %. Residence timeswere about 3 hours in the first reactor and about 2.2 hours in thesecond reactor. The production rate of polymer was about 13.6 kg/hr. Thepolymer was discharged from the reactor as a granular product having anMFR of 3.9 dg/min. and a comonomer content of 1.1 wt % ethylene.

[0178] The molecular weight distributions of the metallocene-basedpolymers (Samples 1-5) are shown in FIG. 1. Samples 4 and 5 are derivedfrom a single metallocene-based catalyst, while Samples 1, 2A, 2B and 3are derived from a two metallocene-based catalyst. Samples 4 and 5(homopolymer and ethylene copolymer respectively) showcharacteristically narrow molecular weight distributions, typical ofsingle site metallocene catalyzed polymers. No differences in molecularweight distribution are observed between homopolymer Sample 4 andethylene copolymer Sample 5. Of the two-metallocene catalyzed polymers,homopolymer Sample 3 shows a modestly broadened molecular weightdistribution, reflecting contributions from the two individualmetallocenes.

[0179] Surprisingly, the invention polymers, Samples 1, 2A and 2B showan unexpected bimodal molecular weight distribution. The incorporationof ≦1 wt % ethylene comonomer during the polymerization process resultsin a substantial broadening of the molecular weight distribution at thehigh molecular weight end. This is unexpected since with both theindividual metallocenes, molecular weight drops with ethylene addition.

[0180] A comparison of the molecular weight distribution of an inventionpolymer (Sample 2A) versus one made by the same process (i.e., additionof ethylene comonomer in a separate polymerization stage) but using aconventional Ziegler-Natta catalyst (Sample 6) is shown in FIG. 2. Theextent of molecular weight broadening to the high end for the inventionpolymer is clearly visible.

[0181] This substantial molecular weight broadening at the highmolecular weight end for the invention polymers can be characterized byseveral techniques, one of which is the measurement of recoverablecompliance (see FIGS. 1 and 2), the value of which is well known totrack the high molecular weight end species of the distribution. Thecompliance values are observed to increase from 1.1×10⁴ Pa⁻¹ for Sample4 (single metallocene; homopolymer) to 3.6×10⁴ Pa⁻¹ for Sample 3 (twometallocenes; homopolymer) to ≧3.9 for invention polymers Samples 1, 2A,and 2B (two metallocenes; copolymer).

[0182] The incorporation of ethylene in the invention polymers, believedto occur primarily in the larger molecules, broadens the meltingdistribution as is seen in the DSC melting data shown in FIG. 3 whichcompares invention polymer, Sample 2A, with metallocene control, Sample4, and Ziegler-Natta control, Sample 6. Single site metallocene-basedcatalysts are known to provide uniform comonomer incorporation among allthe molecules in a polymer sample and to allow greater melting pointdepression than conventional Ziegler-Natta based catalysts for the samecomonomer incorporation level. Even with the greater level of ethyleneincorporation in the invention polymers versus comparable Ziegler-Nattacontrols (0.8 and 1.0 wt % in Samples 1 and 2A versus 0.55 and 0.4 wt %in Samples 6 and 7), the extractables levels in the invention polymersare lower, reflecting their single site catalyzed origin (Table 1).

[0183] The invention polymers (Samples 1, 2A and 2B), twometallocene-catalyzed controls (Samples 3 and 4) and two Ziegler-Nattacatalyzed controls (Samples 6 and 7) were converted to biaxiallyoriented films to assess ease of stretching and orientation. This stepis recognized to be the critical point in the fabrication of suchoriented films. One of the procedures adopted was one that is widelyused in the art and involved cast extrusion of a sheet of polymer(typically 500 μm to 650 μm thick) followed by biaxial orientation atelevated temperature on a stretching apparatus such as a film stretcherfrom the T M Long Co., Somerville, N.J. (henceforth referred to as T MLong machine) to yield a final thickness of 15 μm to 25 μm. Ease of filmstretching or orientation was judged from the uniformity of stretching(i.e., even stretch versus the presence of stretch bands), film saggingand in the most severe case, film breakage. A desired stretching profileis one that offers even stretching, without any stretch bands, breakageor sagging over a wide range of stretching temperatures. The stretchingperformance for the selected polymers are summarized in Table 2. Thesingle metallocene catalyzed homopolymer Sample 4 shows poorstretchability. The two metallocene homopolymer, Sample 3, shows animprovement, though it is not as good as the invention polymers, Samples1, 2A and 2B, which show a desirably broad stretching window. Theperformances of Samples 2A and 2B are seen to be superior to those ofthe Ziegler-Natta controls, Samples 6 and 7.

[0184] Graphical representations of the comparative processabilityranges for the different samples are shown in FIG. 4. A curve having aswide a well as possible would be reflective of a polymer of goodprocessing latitude. FIG. 4A compares the standard metallocene singlesite-based polymer Sample 4 versus the Ziegler-Natta control Sample 6.The lower melting, narrowly distributed polymer Sample 4 can beprocessed at lower temperature than control Sample 6, but it is seen tohave poor processing latitude with stretching temperature. FIG. 4Bcompares the same Ziegler-Natta control Sample 6 against metallocenepolymer, Sample 2A, the invention polymer. The processability range forSample 2A is now seen to be quite a bit broader, particularly at lowstretching temperatures, reflecting very favorable processing latitude.

[0185] Film property measurements on some of the biaxially stretchedfilms produced above are shown in Table 3. The properties of theinvention polymer films compare favorably with the Ziegler-Nattacontrol. The Ziegler-Natta film has slightly higher film stiffness. Ithas been found that the stretching temperature for optimum filmproperties (low haze, maximum stiffness) for the invention polymers islower than that used typically for the Ziegler-Natta control film. Asseen in Table 3, the haze and modulus of the Sample 2A film are bothimproved on going from 154.4° C. stretching temperature to 143.3° C.

[0186] To attain such lower stretching temperatures with today'sZiegler-Natta polymers, one can use random copolymers of similar meltingtemperature to the invention polymers. This was done using Sample 8, a 2MFR, 2.8 wt % ethylene random copolymer with Tm=146° C., the same asinvention polymers Samples 1, 2A and 2B. Biaxially oriented film wasprepared from Sample 8 by extruding cast sheet and stretching it at thelower temperature of 143.3° C. on the T M Long stretching apparatus.Film properties on stretched films of Sample 8 are compared versus thosefor Sample 2A in Table 4. The film properties profile displayed by therandom copolymer Sample 8 is seen to be deficient to that of theinvention polymer. Film stiffness, moisture barrier and tensileproperties are all lower than those for the invention polymer. The filmdata demonstrate the unique balance of favorable film stretchabilitycoupled with good film properties for the invention polymer.

[0187] Additional biaxial stretching measurements using an Instronmachine (Model 1122) were conducted on a similar set of polymerspreviously analyzed via T. M. Long stretching. The key difference is thesimultaneous biaxial stretching provided by the T. M. Long machineversus a sequential stretching provided by the Instron machine.

[0188] The stretching measurements on the Instron were conducted asfollows: Cast extruded sheet (typically 600 μm thick) was cut along themachine direction (MD) into strips 76.2 mm wide. A strip was grippedbetween the jaws on the Instron. An appropriate length of strip was cutto allow a jaw separation of 25.4 mm. The sample was maintained in anenvironmental chamber on the Instron at a temperature of 110° C. Thetemperature thermocouple probe was positioned adjacent to the sample.The sample was stretched to 700% along the MD in the Instron at atemperature of 110° C. and a stretching rate of 50.8 mm/min. After theMD stretching, the sample was held at 700% extension while the chamberdoors were opened and the sample allowed to cool down to ambienttemperature. The sample (about 100 μm thick) was removed from thechamber and cut along the original transverse direction (TD) into 25.4mm wide strips. A strip of appropriate length was again gripped betweenjaws on the Instron. Two different TD stretching conditions were used.

[0189] Case 1: 25.4 mm jaw separation, 1,100% TD stretching ratio, 508mm/min. stretching speed, different stretching temperatures varying from100° C. to 150° C. The strain rate for this stretching condition isabout 2,200% per minute.

[0190] Case 2: 12.7 mm jaw separation, 2,200% TD stretching ratio, 1270mm/min. stretching speed, different stretching temperatures varying from120° C. to 160° C. The strain rate for this stretching condition isabout 11,000% per minute.

[0191] Not all the samples were able to endure these TD stretchingconditions and remain unbroken. Breaks were noted down in the datameasurements when they occurred, along with the tensile strengths at1,100% and 2,200% stretch ratios if unbroken. Two test specimens perpolymer sample were evaluated at each stretching condition; valuesreported are averages for the two specimens.

[0192] TD stretching data per the testing conditions of Case 1 above areshown in Table 5. Table 5 shows the TD tensile strengths at 1,100%stretching ratio, and the break points for those samples that brokeprior to achieving this stretching level. For all the samples, thepropensity to break before reaching 1,100% TD stretching is greater atthe lower temperatures. The superiority of the invention polymers isclearly seen in the data. They withstand breaking much better thaneither the metallocene controls (Samples 3 and 4) or the Ziegler-Nattacontrols (Samples 6 and 7). One has to go down to a stretchingtemperature of 110° C. (25° C. lower than the best of the controlsamples) before a break is noted in the invention polymer films. Also,when comparing samples at temperatures where breakage does not occur(see data at 150° C., for example), the invention polymer films (Samples1 and 2A) show lower tensile strengths (i.e. easier stretchability) at1,100% stretch ratio. Easier TD stretchability at lower stretchingtemperatures, without breaking, is one of the unique features offered bythe invention polymers. Since film breaks during TD stretching aretypically the weak link in biaxially oriented polypropylene filmfabrication, via the tenter frame process, the invention polymers offera significant processing advantage.

[0193] A typical commercial tenter frame process to make biaxiallyoriented polypropylene film, operating at 250 m/min. line speed and withTD stretch ratio 850% (i.e. 1 m wide film stretched to 8.5 m), has aTD-stretch strain rate of about 15,000% per minute. While it isdifficult to match this value in a laboratory test, the Instron TDstretch test conditions of Case 2 above provide a strain rate of 11,000%per minute, which approaches that of the commercial fabrication process.Data measurements per Case 2 conditions are shown in Table 6. Theresults are the same as those noted earlier: Low TD tensile strengthvalues and no film breaks for the invention polymers down to stretchingtemperatures 30° C. lower (130° C. versus 160° C.) than the best of theZiegler-Natta control samples. At high TD strain rates, approachingthose encountered during commercial tenter frame processing, theinvention polymers display better low temperature TD stretchabilitywithout breaking.

[0194] Testing of the processability of the invention polymers duringbiaxially oriented film fabrication via the tenter frame process, wasconducted on a pilot line capable of 1 m wide trimmed films. Thepreparation of such films is readily done using techniques well known inthe art. Invention polymer Sample 2B was compared against Ziegler-Nattacontrol Sample 9. Typical values set for some key processing parameterswere: Sample 2B Sample 9 (1.7 MFR, (2.1 MFR, 159° C. T_(m)) 147° C.T_(m)) Extrusion Melt Temperature 274° C. 269° C. MD Oven Temperature135° C. 122° C. MD Stretching Ratio 5.0 5.1 TD Oven Temperature 182° C.166° C. TD Stretching Ratio 7.7 7.7 Film Thickness 20 μm 20 μm

[0195] A desirable processability range is the range of TD oventemperatures over which good film quality and uniformity are maintained.This was done because in the tenter OPP film process, TD stretching isusually the most critical step when stretch ratio, rate and contour areconstant. At low TD oven temperature, the film is too strong to bestretched evenly and it breaks. At high TD oven temperature, the film istoo soft and weak to withstand stretching; it tends to sag leading topoorly formed film or breakage. So there is a desirable temperaturerange (processability range) to achieve uniform and good quality film. Apreferred resin provides a greater processability range. The data forSamples 9 and 2B are shown in FIG. 5. The processability range for theinvention polymer, Sample 2B, is substantially broader than for theZiegler-Natta control, Sample 9. For example, at a processing qualityindex that provides a processability range of 15° C. (174-189° C.) forSample 9, the corresponding processability range for Sample 2B is 28° C.(150-178° C.). The invention polymer provides no only greater processinglatitude, but also the capability to operate at significantly lower TDoven temperatures. This indicates advantages of lower energy input andhigher line speed potential.

[0196] This superior stretching performance over a wide range of strainrates and temperature is a key attribute of the invention polymers. Ittranslates to a broader biaxially oriented film processability rangeversus today's best Ziegler-Natta propylene polymers and versus singlemetallocene-catalyzed propylene polymers. This processing advantage isaccompanied by a good profile of film properties.

[0197] Although the Examples in this invention deal primarily withfilms, it will be instantly recognized that the attributes of theinvention polymers will lend themselves to use in other end-applicationareas as well. For example, in thermoforming and blow molding, theincreased melt strength derived from the broadening of distribution tothe high molecular weight end, coupled with the easier orientability atlower temperatures, should result in performance benefits versus singlemetallocene-catalyzed propylene polymers. TABLE 1 Description ofSamples* Comonomer Melting Hexane Extractables TREF Extractables SampleCatalyst MFR (wt %) Temp. (C.) (wt %) (wt %) 1 2 MCN 2.1 C₂ (0.8) 147.11.0 3.8 2A 2 MCN 1.0 C₂ (1.0) 146.5 0.9 3.9 2B 2 MCN 1.7 C₂ (0.8) 146.7— 2.5 3 2 MCN 2.0 None 151.0 0.7 — 4 1 MCN 4.3 None 151.0 0.3 — 5 1 MCN3.9 C₂ (1.1) 139.0 0.4 — 6 Z-N 2.6 C₂ (0.55) 157.1 3.2 7.6 7 Z-N 3.4 C₂(0.4) 156.3 3.1 5.9 8 Z-N 2.0 C₂ (2.8) 146.0 3.5 — 9 Z-N 2.1 C₂ (0.6)158.5 — —

[0198] TABLE 2 Biaxially Oriented Film Processability* StretchingTemperature Sample 4 Sample 3 Sample 1 Sample 2A Sample 2B Sample 6Sample 7 (° C.) (Tm = 151° C.) (Tm = 151° C.) (Tm = 147.1° C.) (Tm =146.5° C.) (Tm = 146.7° C.) (Tm = 157.1° C.) (Tm = 156.3° C.) 140.6 B U143.3 B U B E U 146.1 B E E B 148.9 U E U E E B B 151.7 E E E B U 154.4E E E E E U E 157.2 E E S E E 160.0 S S S E E E 166.0 S S

[0199] TABLE 3 Biaxially Oriented Film Properties* Film Property Sample4 Sample 3 Sample 1 Sample 2A Sample 2A+ Sample 2B** Sample 6 Thickness,μm 18 18 18 15 18 15 15 Haze % 1.0 0.9 0.9 1.0 0.3 0.3 0.3 Gloss % 92 9492 91 94 94 94 WVTR @ 37.8° C. & 5.7 5.9 6.5 7.1 6.7 6.9 6.5 100% RH,g/m²/day per 25.4 μm 1% Sec. Modulus, MPa 2130 (309)  2247 (326)  2185(317)  2289 (332)  2359 (342)  2346 (340)  2729 (396)  (kpsi) UltimateTensile Strength, 179 (26)  193 (28)  186 (27)  200 (29)  200 (29)  209(30)  207 (30)  MPa (kpsi) Ultimate Elongation, % 61 70 62 65 65 75 71

[0200] TABLE 4 Biaxialy Oriented Film Properties Comparison* FilmProperty Sample 2A Sample 8 Thickness, μm 18 18 Haze, % 0.3 0.2 Gloss, %94 95 WVTR @ 37.8° C. & 100% RH, g/m²/day 6.7 8.3 per 25.4 μm 1% Sec.Modulus, MPa (kpsi) 2359 (342)  1851 (268)  Ultimate Tensile Strength,MPa (kpsi) 200 (29)  170 (25)  Ultimate Elongation, % 65 72

[0201] TABLE 5 Instron TD Tensile Strength (MPa) per Case 1 StretchingConditions TD Stretching Temperature Sample 4 Sample 3 Sample 1 Sample2A Sample 6 Sample 7 (° C.) (Tm = 151° C.) (Tm = 151° C.) (Tm = 147.1°C.) (Tm = 146.5° C.) (Tm = 157.1° C.) (Tm = 156.3° C.) 100 B B(1,025%)110 B (970%) 9.8 120 8.2 7.5 130 B B 6.6 7.4 B B 135 B B 6.3 6.4 B B(935%) 140 B B (1,050%) 4.5 5.3 B 6.0 145 B 6.3 3.2 — B (965%) 5.0 150 B(900%) 5.1 3.1 3.7 5.1 4.8

[0202] TABLE 6 Instron TD Tensile Strength (MPa) per Case 2 StretchingConditions Sample 1 Sample 2A Sample 6 Sample 7 TD Stretching Temp. (°C.) (T_(m) = 147.1° C.) (T_(m) = 146.5° C.) (T_(m) = 157.1° C.) (T_(m) =156.3° C.) 120 B(1,365%) B(2,100%) B B 130 8.5 8.9 B B 140 5.1 6.1 B B150 3.4 3.0 B(1,965%) B(1,765%) 160 — — 2.9 1.8

[0203] While the present invention has been described and illustrated byreference to particular embodiments, it will be appreciated by those ofordinary skill in the art that the invention lends itself to manydifferent variations not illustrated herein. Additionally, allreferences, standard test methods, patents, applications, etc. areherein incorporated by reference in their entirety.

We claim:
 1. A crystalline propylene polymer composition comprising: (a)from 10 to 90 weight percent of a crystalline propylene homopolymercomposition comprising a first propylene homopolymer and a secondpropylene homopolymer; and (b) from 90 to 10 weight percent of acrystalline propylene copolymer composition comprising a first propylenecopolymer and a second propylene copolymer, the first propylenecopolymer and second propylene copolymer comprising from 0.05 to 15weight percent (based on the total weight of the crystalline propylenepolymer composition) of a comonomer; wherein the crystalline propylenepolymer composition has a molecular weight distribution (Mw/Mn) in therange of from 2.1 to 10; and wherein the propylene homopolymercomposition and the propylene copolymer composition are obtained inseparate stages using a single metallocene catalyst system comprisingtwo different metallocene catalyst components.
 2. The composition ofclaim 1, wherein the comonomer weight percent is in the range of from0.1 to 10.0.
 3. The composition of claim 1, wherein the comonomer isselected from the group consisting of ethylene, 1-butene, 1-pentene,1-hexene, and 1-octene.
 4. The composition of claim 1, wherein theweight percent of the crystalline propylene homopolymer composition isfrom 20 to 80 weight percent.
 5. The composition of claim 1, wherein themolecular weight distribution is from 2.5 to 7.0.
 6. The composition ofclaim 1, wherein the hexane extractables level is less than 2.0 wt % asmeasured by 21 CFR 177.1520(d)(3)(ii).
 7. The composition of claim 1,wherein the single metallocene catalyst system further comprises analkyl alumoxane.
 8. The composition of claim 1, wherein the singlemetallocene catalyst system further comprises an alkyl alumoxane andporous support material.
 9. The composition of claim 1, wherein the twodifferent metallocenes catalyst components are represented by theformula:

wherein M is selected from the group consisting of titanium, zirconium,hafnium, vanadium niobium, tantalum, chromium, molybdenum and tungsten;R¹ and R² are identical or different, are one of a hydrogen atom, aC₁-C₁₀ alkyl group, preferably a C₁-C₃ alkyl group, a C₁-C₁₀ alkoxygroup, a C₆-C₁₀ aryl group, a C₆-C₁₀ aryloxy group, a C₂-C₁₀ alkenylgroup, a C₂-C₄ alkenyl group, a C₇-C₄₀ arylalkyl group, a C₇-C₄₀alkylaryl group, a C₉-C₄₀ arylalkenyl group, or a halogen atom; R³ andR⁴ are hydrogen atoms; R⁵ and R⁶ are identical or different, and are oneof a halogen atom, a C₁-C₁₀ alkyl group which may be halogenated, aC₆-C₁₀ aryl group which may be halogenated, a C₂-C₁₀ alkenyl group, aC₇-C₄₀-arylalkyl group, a C₇-C₄₀ alkylaryl group, a C₈-C₄₀ arylalkenylgroup, a —NR₂ ¹⁵, —SR¹⁵, —OR¹⁵, —OSiR₃ ¹⁵ or —PR₂ ¹⁵ radical, whereinR¹⁵ is one of a halogen atom, a C₁-C₁₀ alkyl group, or a C₆-C₁₀ arylgroup;

—B(R¹¹)—, ⁻Al(R¹¹)—, —Ge—, —Sn—, —O—, —S—, —SO—, —SO₂—, —N(R¹¹)—, —CO—,—P(R¹¹)—, or —P(O)(R¹¹)—; wherein: R¹¹, R¹² and R¹³ are identical ordifferent and are a hydrogen atom, a halogen atom, a C₁-C₂₀ alkyl group,a C₁-C₂₀ fluoroalkyl group, a C₆-C₃₀ aryl group, a C₆-C₃₀ fluoroarylgroup, a C₁-C₂₀ alkoxy group, a C₂-C₂₀ alkenyl group, a C₇-C₄₀ arylalkylgroup, a C₈-C₄₀ arylalkenyl group, a C₇-C₄₀ alkylaryl group, or R¹¹ andR¹², or R¹¹ and R¹³, together with the atoms binding them, can form ringsystems; M² is silicon, germanium or tin; R⁸ and R⁹ are identical ordifferent and have the meanings stated for R¹¹; m and n are identical ordifferent and are zero, 1 or 2, m plus n being zero, 1 or 2; and theradicals R¹⁰ are identical or different and have the meanings stated forR¹¹, R¹² and R¹³ and two adjacent R¹⁰ radicals can be joined together toform a ring system.
 10. A crystalline propylene polymer compositioncomprising: (a) from 10 to 90 weight percent of a isotactic crystallinepropylene homopolymer composition comprising a first propylenehomopolymer and a second propylene homopolymer, the isotacticcrystalline propylene homopolymer composition having a molecular weightdistribution of less than 3.0; and (b) from 90 to 10 weight percent of acrystalline propylene copolymer composition comprising a first propylenecopolymer and a second propylene copolymer, the first propylenecopolymer and second propylene copolymer comprising from 0.05 to 15weight percent (based on the total weight of the crystalline propylenepolymer composition) of a comonomer, the crystalline propylene copolymercomposition having a molecular weight distribution of less than 3.0;wherein the crystalline propylene polymer composition has a molecularweight distribution (Mw/Mn) in the range of from 2.1 to 10; and whereinthe isotactic crystalline propylene homopolymer composition andcrystalline propylene copolymer composition are obtained in separatestages using a single metallocene catalyst system comprising twodifferent metallocene catalyst components.
 11. A process for preparing acrystalline propylene polymer composition comprising the steps of: (a)polymerizing propylene in a first stage; (b) copolymerizing propyleneand a comonomer in a second stage; and (c) recovering the crystallinepropylene polymer composition comprising from 0.05 to 15 weight percentof a comonomer (based on the total weight of the crystalline propylenepolymer composition); wherein the steps (a) and (b) are conducted in thepresence of a single metallocene catalyst system comprising twodifferent metallocene catalyst components.
 12. The process of claim 11,wherein the comonomer is selected from the group consisting of ethylene,1-butene, 1-pentene, 1-hexene, and 1-octene.
 13. The process of claim11, wherein the crystalline propylene polymer composition comprises from0.5 to 8 weight percent of the comonomer (based on the total weight ofthe crystalline propylene polymer composition).
 14. The process of claim11, wherein the crystalline propylene polymer composition comprises from0.5 to 5 weight percent of the comonomer (based on the total weight ofthe crystalline propylene polymer composition).
 15. The process of claim11, wherein the two different metallocenes catalyst components arerepresented by the formula:

wherein M is selected from the group consisting of titanium, zirconium,hafnium, vanadium niobium, tantalum, chromium, molybdenum and tungsten;R¹ and R² are identical or different, are one of a hydrogen atom, aC₁-C₁₀ alkyl group, preferably a C₁-C₃ alkyl group, a C₁-C₁₀ alkoxygroup, a C₆-C₁₀ aryl group, a C₆-C₁₀ aryloxy group, a C₂-C₁₀ alkenylgroup, a C₂-C₄ alkenyl group, a C₇-C₄₀ arylalkyl group, a C₇-C₄₀alkylaryl group, a C₉-C₄₀ arylalkenyl group, or a halogen atom; R³ andR⁴ are hydrogen atoms; R⁵ and R⁶ are identical or different, and are oneof a halogen atom, a C₁-C₁₀ alkyl group which may be halogenated, aC₆-C₁₀ aryl group which may be halogenated, a C₂-C₁₀ alkenyl group, aC₇-C₄₀-arylalkyl group, a C₇-C₄₀ alkylaryl group, a C₈-C₄₀ arylalkenylgroup, a —NR₂ ¹⁵, —SR¹⁵, —OR¹⁵, —OSiR₃ ¹⁵ or —PR₂ ¹⁵ radical, whereinR¹⁵ is one of a halogen atom, a C₁-C₁₀ alkyl group, or a C₆-C₁₀ arylgroup; R⁷ is

—B(R¹¹)—, ⁻Al(R¹¹)—, —Ge—, —Sn—, —O—, —S—, —SO—, —SO₂—, —N(R¹¹)—, —CO—,—P(R¹¹)—, or —P(O)(R¹¹)—; wherein: R¹¹, R¹² and R¹³ are identical ordifferent and are a hydrogen atom, a halogen atom, a C₁-C₂₀ alkyl group,a C₁-C₂₀ fluoroalkyl group, a C₆-C₃₀ aryl group, a C₆-C₃₀ fluoroarylgroup, a C₁-C₂₀ alkoxy group, a C₂-C₂₀ alkenyl group, a C₇-C₄₀ arylalkylgroup, a C₈-C₄₀ arylalkenyl group, a C₇-C₄₀ alkylaryl group, or R¹¹ andR¹², or R¹¹ and R¹³, together with the atoms binding them, can form ringsystems; M² is silicon, germanium or tin; R⁸ and R⁹ are identical ordifferent and have the meanings stated for R¹ 1; m and n are identicalor different and are zero, 1 or 2, m plus n being zero, 1 or 2; and theradicals R¹⁰ are identical or different and have the meanings stated forR¹¹, R¹² and R¹³ and two adjacent R¹⁰ radicals can be joined together toform a ring system.
 16. The process of claim 11, wherein the singlemetallocene catalyst system further comprises an alkyl alumoxaneactivator and porous support material.
 17. A film comprising acrystalline propylene polymer composition comprising: a) from 10 to 90weight percent of a crystalline, isotactic propylene homopolymercomposition comprising a first propylene homopolymer and a secondpropylene homopolymer; and b) from 90 to 10 weight percent of acrystalline propylene copolymer composition comprising a first propylenecopolymer and a second propylene copolymer, the first propylenecopolymer and second propylene copolymer comprising from 0.05 to 15weight percent (based on the total weight of the crystalline propylenepolymer composition) of a comonomer; wherein the crystalline propylenepolymer composition is prepared using a single metallocene catalystsystem comprising two different metallocene catalyst components; andwherein the crystalline propylene polymer composition has a molecularweight distribution from 2.1 to
 10. 18. The film of claim 17, whereinthe film is biaxially oriented at least once in at least one direction.19. The film of claims 17, wherein the film is oriented sequentially.20. The film of claims 17, wherein the film is oriented simultaneously.21. A film comprising a crystalline propylene polymer compositioncomprising: a) from 10 to 90 weight percent of a crystalline, isotacticpropylene homopolymer composition comprising a first propylenehomopolymer and a second propylene homopolymer, the crystalline,isotactic propylene homopolymer composition having a molecular weightdistribution of less than 3; and b) from 90 to 10 weight percent of acrystalline propylene copolymer composition comprising a first propylenecopolymer and a second propylene copolymer, the crystalline propylenecopolymer composition having a molecular weight distribution of lessthan 3, the first propylene copolymer and the second propylene copolymercomprising from 0.05 to 15 weight percent (based on the total weight ofthe crystalline propylene polymer composition) of a comonomer; whereinthe crystalline propylene polymer composition has a molecular weightdistribution in the range of from 2.1 to
 10. 22. The film of claim 21,wherein the film is biaxially oriented at least once in at least onedirection.
 23. The film of claims 21, wherein the film is orientedsequentially or simultaneously.